Cylinder not firing

My dad took out the our 95 sl750. He said it ran fine until he hit a couple waves pretty hard and it would only go 20 mph tops when he had the throttle pinned. Long story short I found out that the furthest forward cylinder isn't getting spark to it. I got new plugs but it made no difference. I don't know what to take a look at next. Maybe the plug wires? Or something in the electronics box. Any ideas? Thanks!